1. Field of the Invention
The present invention relates to a substrate processing apparatus and method and a substrate manufacturing method and, more particularly, to a substrate processing apparatus and method for overlapping and contacting two substrates, and a substrate manufacturing method.
2. Description of the Related Art
Two wafers (substrates) are brought into contact with each other, and superimposed to each other by performing anode joining, press processing, annealing, or the like. This method is suitable for manufacturing a wafer having an SOI structure or the like.
FIGS. 11A and 11B are schematic views showing steps in a process of contacting wafers. In this wafer contact, as shown in FIG. 11A, a first wafer 1 is set on a wafer support jig 201 with its contact surface facing upward, and a second wafer 2 is softly overlapped on the first wafer 1 with its contact surface facing downward. At this time, the upper wafer 2 floats by a gas (e.g., air or inert gas) between the wafers, as shown in FIG. 11A.
Before the gas between the wafers 1 and 2 is completely discharged, the central portion of the upper wafer 2 is pressed by a press pin 202, as shown in FIG. 11B. Then, the gas between the central portions of the wafers is discharged, and the wafers 1 and 2 contact to each other at the central portion. As the gas between the wafers are gradually discharged toward the peripheral portion, the area of the contact portion increases. Finally, the entire wafers contact to each other.
This method is useful for contacting two wafers without remaining any gas between them, but has the following problems.
The first problem is contamination of the wafers along with alignment of the two wafers. That is, since the upper wafer 2 overlapped floats by the gas between the wafers, the friction of the upper wafer 2 in horizontal movement is very small. For this reason, the upper wafer 2 slips even with a slight inclination of the jig 201. Accurately aligning the two wafers 1 and 2 therefore requires a means for restricting the horizontal movement of the wafer 2.
The jig 201 shown in FIGS. 11A and 11B has a recess which coincides with the shapes of the wafers 1 and 2, and aligns the wafers 1 and 2 while restricting the horizontal movement of the wafers 1 and 2 by the sides walls of this recess. FIG. 12 is a view showing another example of the arrangement of the jig for overlapping the wafers 1 and 2 while aligning them. A jig 205 has a plurality of aligning pins 204 and a press pin 203. The press pin 203 presses the wafers 1 and 2 against the plurality of aligning pins 204 to restrict the horizontal movement of the wafers 1 and 2.
In the method of overlapping the two wafers using the jig shown in FIGS. 11A and 11B or FIG. 12, since the peripheral portion of the wafer is brought into contact with the jig, particles may be produced, the peripheral portion of the wafer may be damaged, and the yield may decrease.
Another problem is posed by variations in wafer press conditions. More specifically, the time interval between overlapping of two wafers and pressing of them by the press pin changes, and the gap between the wafers in pressing the wafers by the press pin varies. Therefore, the quality of the wafer obtained by contacting the two wafers is difficult to be made uniform. The gas between the wafers may be partially discharged before the wafers are pressed by the press pin. In this case, the gas may remain between the wafers because the wafers cannot be contacted while the gas is gradually discharged from the central portion toward the peripheral portion.